Hot gas generators have long been utilized for producing hot gas under pressure to operate engines of various sorts as well as for other purposes. See, for example, U.S. Pat. No. 1,828,784 issued Oct. 27, 1931 to Perrin which constitutes the most pertinent prior art known to the applicant.
In such hot gas generators, a carbonaceous fuel is combusted with an oxidant to produce hot gasses of combustion. In addition, additional fuel may be introduced into the hot gasses of combustion to be vaporized, or partly decomposed, or both, (dependent on gas temperature) as opposed to combusted, to increase the volume of hot gas while bringing the temperature of the gas down to some desired temperature incapable of causing damage to the system in which the generator is used.
One difficulty in the operation and use of such hot gas generators is carbon buildup. Carbon buildup results when the fuel is not completely oxidized and elemental carbon is formed within the combustion chamber of the generator. It may deposit itself at various locations therein, particularly those running at relatively cool temperatures. While carbon buildup can be avoided by providing the generator with an excess of oxidant, this results in excessive consumption of oxidant. As ordinarily there is a plentiful supply of liquid fuel, it is normal practice to run a hot gas generator on the rich side so that all oxidant available for combustion is consumed to minimize the consumption of oxidant; and this raises the potential for carbon buildup.
As pointed out by Perrin in his previously identified U.S. Letters Patent, it is also desirable to cool the combustion chamber to prevent damage thereto by excessive heat from combustion occurring therein. Advantageously, this is accomplished by cooling the combustion chamber with fuel. However, in the Perrin construction, there is the opportunity for excessive cooling of the combustion chamber walls; and the resulting cool spots facilitate carbon buildup when the generator is operated on the rich side as is desired to prevent the existence of hot spots.
Carbon buildup is undesirable because it may interfere with heat transfer. However, another problem resulting from carbon buildup is much more serious. Specifically, such hot gas generators are frequently used to produce hot gasses for driving turbine wheels. As carbon builds up, particles of the same typically break free and then flow with the hot gas through the turbine wheel. Such particulate carbon erodes the turbine nozzles and the turbine wheels. Furthermore, carbon deposits can build up on the surfaces of the turbine nozzles and restrict the flow to cause performance losses.
The hot gas generators disclosed in the referenced copending applications avoid many of these difficulties and are accordingly highly advantageous. Nonetheless, improvements in terms of simplifying the construction, assuring full and complete vaporization of fuel introduced downstream of the main combustion zone, and minimizing the number of obstructions in the gas flow zone are desirable.
The present invention is directed to providing the above improvements.